There are more than four thousand flexible dams in the world. Most of them are of the air or water bag types. They can be “opened” (deflated, or collapsed) during rainy seasons, and have numerous advantages over solid dams due to low capital cost, versatility in application, and less impact on environment. However, they have a big disadvantage, they can only be built as low-head dams. Almost all of the current flexible dams are shorter than 5 meters high, beyond which, it becomes impractical, uneconomical and gradually impossible.
One of the objectives of present invention is to provide a new concept for constructing a higher and larger flexible wall dam.
There were several attempts to build a collapsible and more economical flexible wall dam by using non-inflatable type structure, but they had shortcomings, such as:
U.S. Pat. No. 4,906,134 issued to Hoyeck described a flexible wall dam destined to open and close the flow of water, which consisting of an upstanding flexible wall having a common supporting cable above the top edge of the dam, and having solid, telescopic anchoring ties with solid spacers, and having its common supporting cable being extendable for pulling in or releasing, thereby enable this flexible wall dam to open or close the flexible wall for controlling the flow of water. It is noticed that said common supporting cable generally is heavily stressed and sustains the major pulling forces alone the top portion of the flexible wall dam, so the extendable moving mechanisms have to be strong and costly, and said solid telescopic ties and spacers are complicated in construction and operation. All of those issues make this dam expensive to build, maintain, and operate. That is why it is only good for a small dam.
Present invention will provide a new “opening” and “closing” operational methods for a non-inflatable type collapsible flexible wall dam, without extending or retracting the heavily stressed common supporting cable, and without the complexity of the solid tie and spacer elements.
In U.S. Pat. No. 4,906,134 issued to Hoyeck, U.S. Pat. No. 4,647,250 issued to Howard, and U.S. Pat. No. 495,788 issued to L. Debarle, they provided a technique to strengthen a flexible wall dam by connecting multiple reinforcing cables to multiple reinforced joint points on the upstream side of the flexible wall, and anchored to the waterbed of the dam. It is noticed that for a loaded dam, those reinforced joint points and reinforcing cables located on the upstream side of said flexible wall will be submerged into water and will be heavily stressed, so they need more maintenance efforts. Having reinforced joint points and anchors in the water will be a costly arrangement for a flexible wall dam.
Present invention will provide three methods to solve above problems by disposing all the heavily stressed cables and the complicated joints on the dry (downstream) side of the dam. Said methods will greatly reinforce the strength of the flexible wall dam, provide a strong outer “skin” for penetration protection, and avoid dealing with the troublesome water when performing the maintenance works on the reinforcement elements. This will also make it possible to build a stronger, higher, and larger collapsible flexible wall dam and will be economically feasible.
Furthermore, the reinforcement methods provided in this invention are so versatile that they can be applied to both the collapsible and non-collapsible flexible wall dams.